In message , John Rumm
writes
Steven Briggs wrote:
Wall & roof framing I'm thinking 25x75 sawn timber studs & rafters,

50x75 for the framing will give a really solid frame and a bit more
space to play with for insulating and adding electrics etc if required.


I've just been down the timber yard, sawn 25x75 is a bit scaggy. 2nd
choice was CLS, but they only have 2.4m in stock. So 50x75 regularised
carcassing it is. It'll work out the same cost as CLS when wastage is
taken in to account.

50x75 sill & head. Inside skinned with 6mm WBP ply, outside with VT&G

50x100 ridge beam, 19mm shiplap cladding, 12mm WBP ply on the inside -
as Andy suggests it is nice and easy to fix things to after.

I think if it were my shed, I'd use 12mm, but I don't think there'll be
much, if anything, hung of the walls in this case. 6mm is much easier to
handle single-handed too.

weatherboard. I'll put about 30mm of Celotex / Kingspan on the inside
face of the wall cavity. I'm debating the need to vent the remaining
cavity to the outside, I can easily have a 10mm hidden gap around the
framing at ground & eaves level, and over the roof ridge board. Is
this a good idea? Should I put a vapour barrier in there somewhere?
If so, what to use?

Not suggesting this is the best way - but I went for 50mm jabfloor
(cheaper than celotex - but not quite as good - so your 30mm will
probably be as good or better). I fitted it flush with the outside of
the framing so that it formed a vapour barrier next to the shiplap -
that then left 25mm of space inside the warm/dry area for all the
electrics I wanted installed in/under the interior ply.


I thought Jabfloor was polystrene, i.e. not to be in contact with PVC
wiring?


Stick some diagonal cross braces in the wall stud work as it will make
the whole thing much more rigid and will prevent any of the framing
leaning or skewing. I ended up using only half the amount that you see
on the drawings - as that seemed to be enough - but doing some is well
worth it. While on the topic, stick a couple of cross braces between
some of the rafters - this will convert the load of the roof (and
anyone on it!) into a downward thrust rather than a "splaying" thrust
that would otherwise tend to push the walls out. Note also three layers
of roofing felt is heavy!

Good tip, I hadn't thought of diagonals, but it will make a huge
difference. There's already a divider wall that'll brace the side walls,
and I was thinking of another one or two cross braces as well.


Anyway if you want the whole saga you can read it he-

http://www.internode.ltd.uk/workshop/



Thanks John.

--
Steve